It depends on what's most appealing to you.
The fittest females will tend to be at stores like Whole Foods, Sprouts, and Trader Joe's. There are also some example's of regional grocers with a similar profile to those stores mentioned, such as AJ's Fine Foods in Arizona or Central Market in Texas.
The problem with doing seduction at Whole Foods is that while there are some attractive women there, a lot of the women who shop at Whole Foods have attitude problems. There are a lot of careerist, Girl Boss types at Whole Foods. These types are a little bit more difficult for something medium to longer term. Some men might be able to put up with them enough for some short term sex. It all depends on the individual man's preferences.
Sprouts is a little bit better than Whole Foods in terms of pricing. Somewhat lower prices. As a result, the women have attitudes that are a little bit more down to Earth.
With every brand of grocer, some store locations are going to be better for pickup than others. Store locations in neighborhoods with mostly single family houses and a lot of married people are going to be worse options for grocery store approaching. Store locations near apartments and in neighborhoods with mostly unmarried people are where you want to do your grocery store approaching. In a larger metropolitan area, sometimes small distances can make a difference in picking which grocery store you'll want to go to if you want to try and do approaches while out shopping.
In considering my history with grocery store approaching, I have done a lot of grocery store approaching in my life across brands of grocery stores. I have gotten more dates at Kroger/Albertsons branded stores (see links below for list of those store brand names) as compared to Trader Joe's, Whole Foods, Sprouts, or Natural Grocers. That may be something specific to me and my approaching/vibe.
en.wikipedia.org
en.wikipedia.org